LASIK, SMILE or PRK: what each laser does, for the parent who is asking for themselves
You have worn glasses for twenty years and your child is in them now. Here is what LASIK, SMILE and PRK each do to the eye, what comes before any of them, and what the laser cannot change.
- LASIK cuts a thin flap and reshapes the cornea under it, PRK removes the surface layer instead, and SMILE (small incision lenticule extraction, with SMILE Pro the newer Zeiss version) takes out a thin disc of tissue through a small opening with no flap.
- The FDA says "The same type of laser is used for LASIK and PRK"; the real difference is how the middle layer of the cornea is reached.
- A meta-analysis found dry eye after both SMILE and femtosecond LASIK "usually occurs transiently", and the AAO says almost everyone who has LASIK will have dry eyes, usually fading within a month.
- Laser does not change the length of the eye, so retinal checks continue after high myopia, and it does not stop reading glasses: the AAO says "LASIK cannot correct presbyopia."
- Refractive surgery is done by an ophthalmologist; check the National Specialist Register, ask about touch-ups in writing, and expect the assessment to decide the procedure.
If you have worn glasses for twenty years, and your child has now joined you in them, you have probably searched the same three words everyone does: LASIK, SMILE, PRK. They are not three brands of the same thing. They are three different ways of reaching the same layer of the eye, and the differences are worth knowing before you sit in front of a refractive surgeon.
What do these laser operations actually do to the eye?
All three reshape the cornea, the clear front window of the eye, so that light focuses on the retina without the help of glasses. They do not touch the retina, the lens inside the eye or the length of the eyeball. The reshaping is planned from measurements taken before the day, and the whole job is to remove a precise amount of tissue in a precise pattern.
The differences are in how the surgeon gets to the middle layer of the cornea (the stroma) where the reshaping happens. The US Food and Drug Administration (FDA) describes it this way: "In PRK, the top layer of the cornea, called the epithelium, is scraped away to expose the stromal layer underneath. In LASIK, a flap is cut in the stromal layer and the flap is folded back." The FDA adds that "The same type of laser is used for LASIK and PRK." SMILE takes a third route, covered below.
The action for you: when a surgeon recommends one of the three, ask which layer is being opened and why that route suits your eyes. A good answer is specific to your corneal measurements.
How does LASIK work, and what is it good for?
LASIK (laser-assisted in situ keratomileusis) first makes a thin hinged flap on the front of the cornea. The surgeon folds it back, the excimer laser reshapes the tissue underneath, and the flap is laid down again. The American Academy of Ophthalmology (AAO) says the flap "reattaches on its own" within a few minutes. The flap is cut either with a blade or with a femtosecond laser, and your surgeon will say which.
It is the best known of the three, and it treats short-sightedness (myopia, rabun jauh), long-sightedness and astigmatism. Its limits come mostly from the flap and the dry eye that follows. The AAO says "Almost everyone who has LASIK will have dry eyes and changing vision during the day. These symptoms usually fade within a month." The FDA lists flap-related and other risks among its patient pages, and warns that "Some patients may develop severe dry eye syndrome" which "may be permanent".
Because the flap is a permanent change to the cornea, people with a job or sport with a risk of a blow to the eye are asked to think about it carefully. The action: tell the surgeon about contact sports, military or similar work, and about every episode of dry eye you have had.
What are SMILE and SMILE Pro, and how are they different?
SMILE stands for small incision lenticule extraction. A femtosecond laser shapes a thin disc of tissue (the lenticule) inside the cornea, and the surgeon takes it out through a small opening, so there is no flap. SMILE Pro is the name of a newer, faster version of the same lenticule-extraction approach from the manufacturer Zeiss. If a clinic uses either name, the generic description is the same: lenticule extraction, no flap.
What do the studies say? A meta-analysis of dry eye after SMILE and femtosecond LASIK concluded that "Dry eye after both SMILE and FS-LASIK usually occurs transiently" and that "SMILE may have milder subjective symptoms". A separate meta-analysis of 1,385 eyes comparing SMILE with wavefront-guided LASIK found that "Both SMILE and WFG-LASIK were found to be safe, effective, and predictable." In other words, neither is the winner in every way. SMILE avoids a flap but is not suitable for every prescription pattern, and some eyes are better served by LASIK.
The action: ask the surgeon whether your prescription and astigmatism fall in the range their SMILE laser is approved and used for, and what happens if a touch-up is needed afterwards.
When is PRK or another surface laser used?
PRK (photorefractive keratectomy) and its relatives work on the surface. The thin outer layer is removed or moved aside, the laser reshapes the tissue and the surface grows back. There is no flap, which is why surgeons often prefer a surface laser for a thin cornea, or for someone whose work or sport makes a flap a concern.
The price of that is a slower and more uncomfortable start. The surface needs days to heal, vision is hazy longer, and the first days can be sore. The Royal College of Ophthalmologists lists the UK options as LASIK, surface laser (PRK, LASEK, TransPRK) and SMILE, and says the surgeon "will advise on your best treatment options after reviewing your test measurements and your eye health".
The action: if a surface laser is advised, plan more time off screens and demanding work than a friend who had LASIK, and follow the drop schedule exactly.
What checks come before any of them?
Every route starts with the same assessment, and the assessment decides more than the choice of laser. The surgeon needs a stable prescription, shown on paper. The age and stability rules are in when a teenager can have laser eye surgery. A map of the cornea checks thickness and shape. The FDA warns that "Performing a refractive procedure on a cornea that is too thin may result in blinding complications", and the AAO lists keratoconus, severe dry eye and extreme prescriptions as reasons laser may not be suitable. Keratoconus, a cone-shaped thinning of the cornea, is explained in keratoconus in teenagers and the eye-rubbing link.
Pupil size is measured too, because large pupils can mean glare and halos at night. And soft contact lenses must be out of the eyes for about two weeks, harder lenses for longer, before the measurements are taken, because lenses change the shape of the cornea.
When the prescription is very high or the cornea too thin, the answer may be a lens placed inside the eye instead, covered in implantable lenses for a high prescription. Being told laser is not for you is a result of the checks working, not a failure.
What do the first weeks feel like?
After LASIK or SMILE, vision is often much better within a day or two, with scratchiness, light sensitivity and fluctuating clarity as the eye settles. After a surface laser, the first days are more uncomfortable and the clear vision arrives more slowly. The AAO figure for dry eyes above is the practical one: expect to use lubricating drops, and expect the view to vary through the day.
You will be given drops to use on a schedule, shields for sleeping, and a list of things to avoid for a while, such as eye make-up, swimming, rubbing the eyes and contact sport. The surgeon will check you the next day and again over the following weeks. Report pain that gets worse, vision that drops, or a red eye that is getting more red, the same day rather than waiting for the booked visit.
What does laser not change, and what are the honest risks?
It does not make a long eye short. A person with high myopia keeps the longer eyeball and the retinal risks that go with it, so retinal checks go on for life, as described in high myopia: what changes once the number gets high. It also does not stop the reading glasses that arrive with age. The AAO is direct: "LASIK cannot correct presbyopia." There are laser approaches built around that problem, and they come with trade-offs of their own, set out in PRESBYOND and blended vision.
The honest numbers. The AAO says "About 9 out of 10 people (90 percent) who have LASIK end up with vision between 20/20 and 20/40" without glasses or contact lenses. That also means some do not. The FDA is plain about the other side: "Some patients lose vision", "You may be under treated or over treated", and "You may still need glasses or contact lenses after surgery". It adds that "Long-term data are not available", because the first laser was approved for LASIK in 1998. The Royal College of Ophthalmologists adds that laser correction "sometimes needs to be repeated" because prescriptions can change at any stage of life.
Laser is elective. Glasses or contact lenses remain a safe choice, and a child at home who is in glasses is a reason for the parent to be careful, not rushed.
Who should do it in Malaysia, and what should I ask?
Refractive surgery is surgery on the eye, and it should be done by an ophthalmologist. In Malaysia you can check that a doctor is a registered specialist in ophthalmology on the National Specialist Register of the Malaysian Medical Council. Costs vary between centres and are not stated here; ask for what is included, including any touch-up, in writing.
Useful questions are which procedure suits your corneal map and why, what the chance of dry eye is for you, what the plan is if you need an enhancement, and who looks after you if there is a problem at night. This page points you to an assessment by a refractive surgeon. It does not recommend any clinic or any procedure.
- Pain gets worse instead of settling, or the eye gets redder.
- Vision drops after it had been improving.
- Light hurts a lot, or there is new discharge.
- The eye is hit, rubbed hard or scratched, especially in the first weeks after a flap.
- A curtain, a shower of floaters or flashes of light appear.
Common questions
What is the difference between LASIK, SMILE and PRK?
What is SMILE Pro?
Is SMILE better than LASIK?
Will I still need reading glasses after laser?
Does laser surgery cause dry eye?
Does laser stop my eyes needing retinal checks?
Who can do laser eye surgery in Malaysia?
- US Food and Drug Administration · What is LASIK? · www.fda.gov
- US Food and Drug Administration · What are the risks and how can I find the right doctor for me? · www.fda.gov
- US Food and Drug Administration · When is LASIK not for me? · www.fda.gov
- American Academy of Ophthalmology · LASIK: laser eye surgery · www.aao.org
- American Association for Pediatric Ophthalmology and Strabismus · Refractive errors in children · aapos.org
- Royal College of Ophthalmologists · Laser Vision Correction, patient information (copy of the leaflet) · bluefinvision.com
- Royal College of Ophthalmologists · Professional standards for refractive surgery · www.rcophth.ac.uk
- PubMed · Dry eye after SMILE versus FS-LASIK for myopia: a meta-analysis (PLoS One 2016) · pubmed.ncbi.nlm.nih.gov
- PubMed · Wavefront-guided LASIK versus SMILE for myopia: systematic review and meta-analysis (Acta Ophthalmol 2023) · pubmed.ncbi.nlm.nih.gov